Biosphere 2
This is Biosphere 2 in the Arizona desert. Constructed between 1987 and ‘89, the ill fated ’self-contained environment’ experiment was supposedly intended to explore the possible use of closed biospheres in space colonisation (you know, like in Total Recall!). The name comes from the idea that it was modelled on “Biosphere 1″, the Earth. Unfortunately it seems that the first inhabitants argued constantly and nearly starved.
It looks like Biosphere 2 is currently available for redevelopment if anyone’s interested… but they also seem to do tours if that’s a little out your league…
Finally, Biosphere 2 featured in the 1996 film Bio-Dome with Pauly Shore and Stephen Baldwin, but David Hill asked me not to mention it. 
Thanks to (deep breath) Jon Anderson, Why Law, Colin Marquardt, Yablo, Roy Tanaka, Jered, Matthew, Chris, Parker, Douglas T. Allbright, David Hill and finally Papapenguin. Phew! Thanks guys 
Actually, I think what happened with Biosphere 2 is that as the concrete that made up the Biosphere aged, it absorbed CO2, so the cycle became unbalanced and screwed up.
Here is an interesting reassesment of the whole thing
http://www.wired.com/wired/archive/12.12/biosphere.html
Ive been there. The deal about the cement is that it had not dried, and it was sucking up the oxygen not carbon dioxide. I actually went inside biosphere in 02, and it was great!
A new book by biospherian, Jane Poynter (The Human Experiment:Two Years and Twenty Minutes Inside Biosphere) is suppose to clarify the CO2 question. There is an excerpt from the book on that subject here: http://janepoynter.com/excerpts.asp